High-density fluidized bed systems

ABSTRACT

Systems and methods for producing an olefin and/or an aromatic via catalytic cracking are disclosed. Naphtha is sub-jected to catalytic cracking conditions in one or more fluidized bed reactors sufficient to produce one or more olefins and/or one or more aromatics. In the fluidized bed reactors, the solid volume fraction of the fluidized bed is in a range of 0.07 to 0.2 and the bulk density of the fluidized bed is greater than 100 kg/m3.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/883,060, filed Aug. 5, 2019, which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

The present invention generally relates to systems and methods for catalytically cracking naphtha. More specifically, the present invention relates to systems and methods for producing light olefins and BTX (benzene, toluene, xylene) via catalytic cracking of naphtha in a fluidized bed reaction unit.

BACKGROUND OF THE INVENTION

Light olefins (C₂ to C₄ olefins) are building blocks for many chemical processes. Light olefins are used to produce polyethylene, polypropylene, ethylene oxide, ethylene chloride, propylene oxide, and acrylic acid, which, in turn, are used in a wide variety of industries such as the plastic processing, construction, textile, and automotive industries. Generally, light olefins are produced by steam cracking naphtha and dehydrogenation of paraffin.

BTX (benzene, toluene, and xylene) are a group aromatics that are used in many different areas of the chemical industry, especially the plastic and polymer sectors. For instance, benzene is a precursor for producing polystyrene, phenolic resins, polycarbonate, and nylon. Toluene is used for producing polyurethane and as a gasoline component. Xylene is feedstock for producing polyester fibers and phthalic anhydride. In the petrochemical industry, benzene, toluene, and xylene are conventionally produced by catalytic reforming of naphtha.

Over the last few decades, the demand for both light olefins and BTX has been consistently increasing. One of the conventional methods for producing light olefins and aromatics (e.g., BTX) includes catalytic cracking of naphtha in a fluidized bed. However, these conventional fluidized bed reactors are generally operated with low average solid volume fraction and low gas-solids contact efficiency due to the limitation of superficial gas velocities in the fluidized bed. Thus, the products of the conventional methods often include a high methane content produced from thermal cracking of hydrocarbons, resulting in increased production cost for light olefins and BTX. Additionally, high backmixing in the conventional catalytic cracking method can further limit the yield of light olefins.

Overall, while methods of producing light olefins and BTX exist, the need for improvements in this field persists in light of at least the aforementioned drawbacks for the methods.

BRIEF SUMMARY OF THE INVENTION

A solution to at least some of the above-mentioned problems associated with the production process for light olefins and BTX via catalytic cracking has been discovered. The solution resides in a method of producing an olefin and/or an aromatic via catalytic cracking of naphtha in a fluidized bed. The fluidized bed has a catalyst volume fraction between 0.07 and 0.2 with an average catalyst bed density greater than 100 kg/m³. This can be beneficial for at least minimizing thermal cracking of hydrocarbons of the naphtha, thereby reducing the production of methane and improving the yields of light olefins and/or aromatics. Furthermore, by reducing thermal cracking, the energy input of the process can be more efficiently utilized for producing light olefins and BTX, resulting in improved energy efficiency. Additionally, the high solid volume fraction (catalyst volume fraction) and high catalyst bed density can reduce backmixing in the fluidized bed reactor and promote reaction kinetics of a plug flow reactor in the fluidized bed reactor, thereby increasing the yields of more valuable light olefins. Therefore, the method of the present invention provides a technical solution to at least some of the problems associated with the currently available methods for producing light olefins and BTX mentioned above.

Embodiments of the invention include a method of producing an olefin and/or an aromatic. The method comprises contacting naphtha with catalyst of a fluidized bed, under reaction conditions sufficient to produce one or more olefins and/or one or more aromatics. The fluidized bed has (1) catalyst volume fraction between 0.07 and 0.2 and (2) average catalyst bed density greater than 100 kg/m³.

Embodiments of the invention include a method of producing an olefin and an aromatic. The method comprises contacting naphtha with catalyst of a fluidized bed, under reaction conditions sufficient to produce one or more of ethylene, propylene, butylene, benzene, toluene, and xylene. The fluidized bed has (1) catalyst volume fraction between 0.07 and 0.2 and (2) average catalyst bed density greater than 100 kg/m³.

Embodiments of the invention include a method of producing an olefin and an aromatic. The method comprises contacting naphtha with catalyst of a fluidized bed, under reaction conditions sufficient to produce one or more of ethylene, propylene, butylene, benzene, toluene, and xylene. The fluidized bed has (1) catalyst volume fraction between 0.07 and 0.2 and (2) average catalyst bed density in a range of 100 kg/m³ to 240 kg/m³.

The following includes definitions of various terms and phrases used throughout this specification.

The terms “about” or “approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.

The terms “wt. %”, “vol. %” or “mol. %” refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol. % of component.

The term “substantially” and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

The terms “inhibiting” or “reducing” or “preventing” or “avoiding” or any variation of these terms, when used in the claims and/or the specification, include any measurable decrease or complete inhibition to achieve a desired result.

The term “fluidized bed” as that term is used in the specification and/or claims, means a type of reactor, in which a gas or liquid fluid is passed through a solid granular material (catalyst) at velocities sufficient to suspend the solid and cause it to behave as though it were a fluid.

The term “riser” or “riser reactor,” or any variation of these terms, where used in the claims and/or the specification, means a type of tubular reactor with a high height-to-diameter ratio, which allows a fluid to mix with a solid catalyst at the bottom of the reactor and rise upwards with close to plug flow behavior.

The term “effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

The use of the words “a” or “an” when used in conjunction with the term “comprising,” “including,” “containing,” or “having” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

The words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

The process of the present invention can “comprise,” “consist essentially of,” or “consist of” particular ingredients, components, compositions, etc., disclosed throughout the specification.

The term “primarily,” as that term is used in the specification and/or claims, means greater than any of 50 wt. %, 50 mol. %, and 50 vol. %. For example, “primarily” may include 50.1 wt. % to 100 wt. % and all values and ranges there between, 50.1 mol. % to 100 mol. % and all values and ranges there between, or 50.1 vol. % to 100 vol. % and all values and ranges there between.

Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows a schematic diagram of a system for producing an olefin and/or an aromatic, according to embodiments of the invention; and

FIG. 2 shows a schematic flowchart of a method of producing an olefin and/or an aromatic, according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Currently, light olefins and BTX can be produced by catalytic cracking of hydrocarbons. However, the overall yield for the target products is relatively low at least partially because thermal cracking of the hydrocarbons during the catalytic cracking process can lead to a portion of the naphtha being converted into methane. This can result in low carbon efficiency by converting naphtha to low valued methane and cause low energy efficiency for the catalytic cracking process due to the energy consumed by thermal cracking. Furthermore, the conventional catalytic cracking process generally includes extensive backmixing of the hydrocarbons and catalyst particles in the fluidized bed, resulting in reduced yields of light olefins. The present invention provides a solution to at least some of these problems. The solution is premised on a method of producing an olefin and/or an aromatic via catalytic cracking of naphtha in a fluidized bed. The fluidized bed has a high solid (catalyst) volume fraction and a high catalyst bed density to limit the occurrence of thermal cracking, resulting in improved carbon efficiency and energy efficiency compared to the conventional methods for catalytic cracking of naphtha. Additionally, this method is capable of reducing backmixing of catalyst particles and the hydrocarbons in the fluidized bed, thereby improving the yields of light olefins compared to the conventional methods. These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. System for Producing Olefins and BTX

In embodiments of the invention, the system for producing an olefin and/or an aromatic can include a fluidized bed reaction unit, a solid-gas separation unit, a catalyst regeneration unit, and a product separation unit. With reference to FIG. 1, a schematic diagram is shown of system 100 that is configured to produce olefins and aromatics with improved carbon efficiency and energy efficiency compared to conventional processes. According to embodiments of the invention, system 100 includes fluidized bed reaction unit 101 configured to catalytically crack hydrocarbon feed stream 11 to produce olefins and/or aromatics.

According to embodiments of the invention, fluidized bed reaction unit 101 includes one or more fluidized bed reactors. Each of the fluidized bed reactors may include a shell. In embodiments of the invention, the shell is made of a material comprising stainless steel, carbon steel, or combinations thereof. In embodiments of the invention, each of the fluidized bed reactors includes a feed inlet disposed on the shell configured to receive feed stream 11 into the shell. In embodiments of the invention, feed stream 11 may include naphtha with a final boiling point lower than 240° C. In embodiments of the invention, each of the fluidized bed reactors includes an outlet disposed on the shell configured to release effluent stream 12 from the shell. According to embodiments of the invention, each of the fluidized bed reactors includes a catalyst inlet disposed on the shell. In embodiments of the invention, the catalyst inlet is configured to receive a catalyst stream 14 into the shell.

According to embodiments of the invention, one or more of the fluidized bed reactors are riser reactors and each of the riser reactors further comprises a lift gas inlet disposed at the lower half of the shell. The lift gas inlet is configured to receive lift gas stream 13 into the shell. In embodiments of the invention, the lift gas inlet may be disposed at a position lower than the feed inlet and the catalyst inlet. Non-limiting examples of the lift gas include nitrogen, methane, any inert gas, or combinations thereof. In embodiments of the invention, lift gas stream 13 includes less than 30 wt. % nitrogen.

In embodiments of the invention, each of the one or more fluidized bed reactors comprises a fluidized catalyst bed disposed in the shell. In embodiments of the invention, the fluidized catalyst bed comprises a catalyst including H-ZSM-5, silica-alumina, or combinations thereof. The catalyst may further comprise a supporting material including amorphous SiO₂, P (Phosphorus), La (Lanthanum), or combinations thereof. In embodiments of the invention, the catalyst has a metal to support ratio in a range of 70 to 90 wt. % and all ranges and values there between including ranges of 70 to 72 wt. %, 72 to 74 wt. %, 74 to 76 wt. %, 76 to 78 wt. %, 78 to 80 wt. %, 80 to 82 wt. %, 82 to 84 wt. %, 84 to 86 wt. %, 86 to 88 wt. %, and 88 to 90 wt. %. The catalyst may have a particle density higher than 1200 kg/m³, preferably 1200 to 1600 kg/m³ and all ranges and values there between including ranges of 1200 to 1240 kg/m³, 1240 to 1280 kg/m³, 1280 to 1320 kg/m³, 1320 to 1360 kg/m³, 1360 to 1400 kg/m³, 1400 to 1440 kg/m³, 1440 to 1480 kg/m³, 1480 to 1520 kg/m³, 1520 to 1560 kg/m³, and 1560 to 1600 kg/m³. According to embodiments of the invention, the fluidized catalyst bed may have a catalyst to oil ratio in a range of 20 to 40 and all ranges and values there between including ranges 20 to 22, 22 to 24, 24 to 26, 26 to 28, 28 to 30, 30 to 32, 32 to 34, 34 to 36, 36 to 38, and 38 to 40. In embodiments of the invention, the fluidized catalyst bed in each of the fluidized bed reactors has a bulk density of greater than 100 kg/m³, preferably 100 to 240 kg/m³ and all ranges and values there between including ranges of 100 to 110 kg/m³, 110 to 120 kg/m³, 120 to 130 kg/m³, 130 to 140 kg/m³, 140 to 150 kg/m³, 150 to 160 kg/m³, 160 to 170 kg/m³, 170 to 180 kg/m³, 180 to 190 kg/m³, 190 to 200 kg/m³, 200 to 210 kg/m³, 210 to 220 kg/m³, 220 to 230 kg/m³, and 230 to 240 kg/m³.

According to embodiments of the invention, system 100 may further include pre-heater 102 disposed upstream to the feed inlet of the fluidized bed reactor. Pre-heater 102 may be configured to heat feed stream 11 and produce heated feed stream 15. The pre-heater may be adapted to heat feed stream 11 to a temperature in a range of 280 to 320° C. and all ranges and values there between including ranges of 280 to 282° C., 282 to 284° C., 284 to 286° C., 286 to 288° C., 288 to 290° C., 290 to 292° C., 292 to 294° C., 294 to 296° C., 296 to 298° C., 298 to 300° C., 300 to 302° C., 302 to 304° C., 304 to 306° C., 306 to 308° C., 308 to 310° C., 310 to 312° C., 312 to 314° C., 314 to 316° C., 316 to 318° C., and 318 to 320° C. In embodiments of the invention, an outlet of preheater 102 is in fluid communication with the feed inlet of the fluidized bed reactor(s) such that heated feed stream 15 flows from preheater 102 to the one or more fluidized bed reactors of reaction unit 101.

In embodiments of the invention, the effluent outlet(s) of the one or more fluidized bed reactors is in fluid communication with an inlet of solid-gas separation unit 103 such that effluent stream 12 flows from the fluidized bed reactor(s) to solid-gas separation unit 103. In embodiments of the invention, solid-gas separation unit 103 is configured to separate effluent stream 12 into spent catalyst stream 16 and gaseous product stream 17. In embodiments of the invention, solid-gas separation unit 103 may include one or more cyclone system. In embodiments of the invention, spent catalyst stream 16 includes the catalyst particles with carbon deposit. Spent catalyst stream 16 may further include additional hydrocarbons absorbed on the catalyst particles.

According to embodiments of the invention, a first outlet of solid-gas separation unit 103 may be in fluid communication with catalyst regeneration unit 104 such that spent catalyst stream 16 flows from solid-gas separation unit 103 to catalyst regeneration unit 104. In embodiments of the invention, catalyst regeneration unit 104 is configured to regenerate spent catalyst from spent catalyst stream 16 to produce catalyst stream 14 that comprises regenerated catalyst. In embodiments of the invention, catalyst regeneration unit 104 includes a regeneration gas inlet adapted to receive regeneration gas stream 18 into catalyst regeneration unit 104. Non-limiting examples of regeneration gas can include air, oxygen, or combinations thereof. In embodiments of the invention, system 100 may further include a stripper disposed upstream to catalyst regeneration unit 104. The stripper may be configured to strip hydrocarbons absorbed on the catalyst particles before spent catalyst stream 16 enters catalyst regeneration unit 104.

In embodiments of the invention, an outlet of catalyst regeneration unit 104 may be in fluid communication with the catalyst inlet of each of the fluidized bed reactors such that regenerated catalyst of catalyst stream 14 flows from catalyst regeneration unit 104 to reaction unit 101. According to embodiments of the invention, makeup catalyst stream 19 containing fresh catalyst particles may be combined with catalyst stream 14 before it flows to reaction unit 101.

According to embodiments of the invention, a second outlet of solid-gas separation unit 103 is in fluid communication with product separation unit 105 such that gaseous product stream 17 flows from solid-gas separation unit 103 to product separation unit 105. In embodiments of the invention, product separation unit 105 is configured to separate gaseous product stream 17 to produce recycle stream 20 and a plurality of product streams. The plurality of product streams can include one or more of an ethylene stream comprising primarily ethylene, a propylene stream comprising primarily propylene, and a BTX stream comprising primarily benzene, toluene, and xylene, collectively. The product streams may further comprise one or more C₄ streams comprising butadiene, isobutene, 1-butene, 2-butene, or combinations thereof. According to embodiments of the invention, recycle stream 20 comprises C₅ to C₁₂ hydrocarbons. Recycle stream 20 may further include C₄ paraffins. According to embodiments of the invention, product separation unit 105 includes one or more quench towers, one or more compressors, one or more BTX extraction units, one or more distillation columns, one or more wash towers, one or more hydrogenation units, one or more caustic towers, one or more acid and oxygen removal units, or any combination thereof.

In embodiments of the invention, an outlet of product separation unit 105 may be in fluid communication with an inlet of pre-heater 102 such that recycle stream 20 combines with feed stream 11 before it is flowed into reaction unit 101. According to embodiments of the invention, multiple fluidized bed reactors of reaction unit 101 can be operated with a single unit of solid-gas separation unit 103, a single unit of catalyst regeneration unit 104, and/or a single unit of product separation unit 105.

B. Method of Producing an Olefin and/or an Aromatic

Methods of producing olefins and aromatics via catalytic cracking of naphtha have been discovered. Embodiments of the method are capable of increasing yields of light olefins and BTX and improving the energy efficiency compared to conventional methods of catalytic cracking. As shown in FIG. 2, embodiments of the invention include method 200 for producing an olefin and/or an aromatic. Method 200 may be implemented by system 100, as shown in FIG. 1.

According to embodiments of the invention, as shown in block 201, method 200 includes contacting naphtha of feed stream 11 with catalyst of a fluidized bed(s) in one or more fluidized bed reactors of reaction unit 101 under reaction conditions sufficient to produce one or more olefins and/or one or more aromatics. In embodiments of the invention, the fluidized bed is disposed in a riser reactor. The contacting at block 201 may include injecting lift gas stream 13, feed stream 11, and catalyst stream 14 into the one or more riser reactors of reaction unit 101 such that hydrocarbons in feed stream 11 make contact with catalyst particles from catalyst stream 14. At block 201, the fluidized bed may have a solid (catalyst) volume fraction in a range of 0.07 and 0.2 and all ranges and values there between including ranges of 0.07 to 0.08, 0.08 to 0.09, 0.09 to 0.10, 0.10 to 0.11, 0.11 to 0.12, 0.12 to 0.13, 0.13 to 0.14, 0.14 to 0.15, 0.15 to 0.16, 0.16 to 0.17, 0.17 to 0.18, 0.18 to 0.19, and 0.19 to 0.20. The solid volume fraction range may be achieved by adjusting superficial gas velocity of feed stream 11 and/or catalyst circulation rate in the fluidized bed reactors. In embodiments of the invention, the fluidized bed has an average catalyst bed density of greater than 100 kg/m³, preferably 100 to 240 kg/m³ and all ranges and values there between including ranges of 100 to 110 kg/m³, 110 to 120 kg/m³, 120 to 130 kg/m³, 130 to 140 kg/m³, 140 to 150 kg/m³, 150 to 160 kg/m³, 160 to 170 kg/m³, 170 to 180 kg/m³, 180 to 190 kg/m³, 190 to 200 kg/m³, 200 to 210 kg/m³, 210 to 220 kg/m³, 220 to 230 kg/m³, and 230 to 240 kg/m³.

At block 201, the riser reactor may be operated with a volumetric ratio between feed stream 11 to lift gas 13 in a range of 60 to 100% and all ranges and values there between including ranges of 60 to 64%, 64 to 68%, 68 to 72%, 72 to 76%, 76 to 80%, 80 to 84%, 84 to 88%, 88 to 92%, 92 to 96%, and 96 to 100%. In embodiments of the invention, at block 201, a superficial velocity in the fluidized bed may be in a range of 1 to 3 m/s and all ranges and values there between 1 to 1.2 m/s, 1.2 to 1.4 m/s, 1.4 to 1.6 m/s, 1.6 to 1.8 m/s, 1.8 to 2.0 m/s, 2.0 to 2.2 m/s, 2.2 to 2.4 m/s, 2.4 to 2.6 m/s, 2.6 to 2.8 m/s, and 2.0 to 3.0 m/s.

In embodiments of the invention, the reaction conditions at block 201 include a reaction temperature in a range of 650 to 700° C. and all ranges and values there between including ranges of 650 to 655° C., 655 to 660° C., 660 to 665° C., 665 to 670° C., 670 to 675° C., 675 to 680° C., 680 to 685° C., 685 to 690° C., 690 to 695° C., and 695 to 700° C. The reaction conditions at block 201 may further include a reaction pressure in a range of 1 to 3 bar and all ranges and values there between including ranges of 1 to 1.2 bar, 1.2 to 1.4 bar, 1.4 to 1.6 bar, 1.6 to 1.8 bar, 1.8 to 2.0 bar, 2.0 to 2.2 bar, 2.2 to 2.4 bar, 2.4 to 2.6 bar, 2.6 to 2.8 bar, and 2.8 to 3.0 bar. The reaction conditions at block 201 may further still include a weight hourly space velocity of 10 to 40 hr⁻¹ and all ranges and values there between including ranges of 10 to 12 hr⁻¹, 12 to 14 hr⁻¹, 14 to 16 hr⁻¹, 16 to 18 hr⁻¹, 18 to 20 hr⁻¹, 20 to 22 hr⁻¹, 22 to 24 hr⁻¹, 24 to 26 hr⁻¹, 26 to 28 hr⁻¹, 28 to 30 hr⁻¹, 30 to 32 hr⁻¹, 32 to 34 hr⁻¹, 34 to 36 hr⁻¹, 36 to 38 hr⁻¹, 38 to 40 hr⁻¹.

According to embodiments of the invention, at block 201, an average contact time between hydrocarbons and catalyst particles in the fluidized bed is in a range of 1 to 3 s and all ranges and values there between including ranges of 1 to 1.2 m/s, 1.2 to 1.4 m/s, 1.4 to 1.6 m/s, 1.6 to 1.8 m/s, 1.8 to 2.0 m/s, 2.0 to 2.2 m/s, 2.2 to 2.4 m/s, 2.4 to 2.6 m/s, 2.6 to 2.8 m/s, and 2.0 to 3.0 m/s. In embodiments of the invention, residence time distribution for the catalyst particles in the fluidized reactors can be characterized as that 95% of catalyst particles have a residence time in a range of 1 to 5 s. According to embodiments of the invention, at block 201, the fluidized bed reactors are operated with reaction kinetics substantially similar to plug flow reactor(s).

In embodiments of the invention, the one or more olefins include ethylene, propylene, 1-butene, 2-butene, isobutene, or combinations thereof. The one or more aromatics include benzene, toluene, xylene, or combinations thereof. In embodiments of the invention, the yields for light olefins (i.e., ethylene and propylene) can be in a range of 30 to 45% and all ranges and values there between including ranges of 30 to 33%, 33 to 36%, 36 to 39%, 39 to 42%, and 42 to 45%. The yields for BTX can be in a range of 10 to 25% and all ranges and values there between including ranges of 10 to 13%, 13 to 16%, 16 to 19%, 19 to 22%, and 22 to 25%. In embodiments of the invention, the contacting at block 201 may further produce C₅ to C₁₂ hydrocarbons that are not BTX.

According to embodiments of the invention, as shown in block 202, method 200 may include separating effluent stream 12 from one or more fluidized bed reactors of reaction unit 101 in solid-gas separation unit 103 to produce gaseous product stream 17 and spent catalyst stream 16. In embodiments of the invention, effluent stream 12 may include the one or more olefins, the one or more aromatics, C₅ to C₁₂ hydrocarbons that are not BTX, unreacted naphtha, lift gas, catalyst particles, or combinations thereof. Gaseous product stream 17 may include one or more olefins, one or more aromatics, one or more C₅ to C₁₂ hydrocarbons that are not BTX, unreacted naphtha, the lift gas, or combinations thereof. Spent catalyst stream 16 may include spent catalyst particles and hydrocarbons absorbed on the spent catalyst particles.

According to embodiments of the invention, as shown in block 203, method 200 includes separating gaseous product stream 17 in product separation unit 105 to produce (i) recycle stream 20 comprising C₅ to C₁₂ hydrocarbons, and (ii) a plurality of product streams including an ethylene stream comprising primarily ethylene, a propylene stream comprising primarily propylene, a BTX stream comprising primarily benzene, toluene, and xylene, collectively, a C₄ hydrocarbon stream comprising one or more of butadiene, isobutene, 1-butene, and 2-butene, or combinations thereof. In embodiments of the invention, the separating at block 203 may include extracting BTX from gaseous product stream 17. The separating at block 203 may further include distilling at least a portion of gaseous product stream 17 in one or more distillation columns to separate ethylene, propylene, and/or the C₄ hydrocarbons stream. In embodiments of the invention, separating at block 203 may include hydrogenating at least a portion of unsaturated C₄ hydrocarbons of the C₄ hydrocarbon stream to produce saturated C₄ hydrocarbons, and separating and flowing the saturated C₄ hydrocarbons as a portion of recycle stream 20.

According to embodiments of the invention, as shown in block 204, method 200 includes recycling recycle stream 20 to the one or more fluidized bed reactors of reaction unit 101. In embodiments of the invention, as shown in block 205, method 200 includes regenerating spent catalyst of spent catalyst stream 16 in catalyst regeneration unit 104 to produce catalyst stream 14 comprising regenerated catalyst. Method 200 may include stripping hydrocarbons absorbed on spent catalyst particles before the regenerating at block 205. In embodiments of the invention, the regenerating at block 205 is conducted at a regeneration temperature in a range of 720 to 750° C. In embodiments of the invention, as shown in block 206, method 200 may include flowing catalyst stream 14 including (1) the regenerated catalyst and/or (2) the fresh catalyst of makeup catalyst stream 19 to the one or more fluidized bed reactors of reaction unit 101.

Although embodiments of the present invention have been described with reference to blocks of FIG. 2, it should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 2. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 2.

In the context of the present invention, at least the following 14 embodiments are described. Embodiment 1 is a method of producing an olefin and/or an aromatic. The method includes contacting naphtha with catalyst of a fluidized bed, under reaction conditions sufficient to produce one or more olefins and/or one or more aromatics, where the fluidized bed has (1) catalyst volume fraction between 0.07 and 0.2 and (2) average catalyst bed density greater than 100 kg/m³. Embodiment 2 is the method of embodiment 1, wherein the one or more olefins include ethylene, propylene, 1-butene, 2-butene, isobutene, or combinations thereof. Embodiment 3 is the method of either of embodiments 1 or 2, wherein the one or more aromatics include benzene, toluene, xylene, or combinations thereof. Embodiment 4 is the method of any of embodiments 1 to 3, wherein the average catalyst bed density is in a range of 100 kg/m³ to 240 kg/m³. Embodiment 5 is the method of any of embodiments 1 to 4, wherein the catalyst particles have a density of at least 1400 kg/m³. Embodiment 6 is the method of any of embodiments 1 to 5, wherein the catalyst of the fluidized bed is located in one or more riser reactors. Embodiment 7 is the method of embodiment 6, wherein the one or more riser reactors are operated using a lift gas containing nitrogen, methane, an inert gas, or combinations thereof. Embodiment 8 is the method of either of embodiments 6 or 7, wherein the fluidized bed has a superficial gas velocity in a range of 1 to 3 m/s. Embodiment 9 is the method of any of embodiments 6 to 8, wherein the one or more riser reactors are operated with reaction kinetics substantially follows plug flow reactors. Embodiment 10 is the method of any of embodiments 1 to 9, wherein the reaction conditions include a reaction temperature of 650 to 700° C. Embodiment 11 is the method of any of embodiments 1 to 10, wherein the reaction conditions include a weight hourly space velocity of 10 to 40 hr⁻¹. Embodiment 12 is the method of any of embodiments 1 to 11, wherein the reaction conditions include an average contact time between naphtha and the catalyst in a range of 1 to 3 s. Embodiment 13 is the method of any of embodiments 1 to 12, wherein the reaction conditions include an operation pressure in a range of 100 to 300 Pa. Embodiment 14 is the method of any of embodiments 1 to 13, wherein the method has a methane yield of less than 10%.

Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. 

1. A method of producing an olefin and/or an aromatic, the method comprising: contacting naphtha with catalyst of a fluidized bed, under reaction conditions sufficient to produce one or more olefins and/or one or more aromatics, where the fluidized bed has (1) catalyst volume fraction between 0.07 and 0.2 and (2) average catalyst bed density greater than 100 kg/m³.
 2. The method of claim 1, wherein the one or more olefins include ethylene, propylene, 1-butene, 2-butene, isobutene, or combinations thereof.
 3. The method of claim 1, wherein the one or more aromatics include benzene, toluene, xylene, or combinations thereof.
 4. The method of any of claim 1, wherein the average catalyst bed density is in a range of 100 kg/m³ to 240 kg/m³.
 5. The method of any of claim 1, wherein the catalyst particles have a density of at least 1400 kg/m³.
 6. The method of any claim 1, wherein the catalyst of the fluidized bed is disposed in one or more riser reactors.
 7. The method of claim 6, wherein the one or more riser reactors are operated using a lift gas comprising nitrogen, methane, an inert gas, or combinations thereof.
 8. The method of claim 6, wherein the fluidized bed has a superficial gas velocity in a range of 1 to 3 m/s.
 9. The method of any claim 6, wherein the one or more riser reactors are operated with reaction kinetics substantially follows plug flow reactors.
 10. The method of any of claim 1, wherein the reaction conditions include a reaction temperature of 650 to 700° C.
 11. The method of any of claim 1, wherein the reaction conditions include a weight hourly space velocity of 10 to 40 hr⁻¹.
 12. The method of any of claim 1, wherein the reaction conditions include an average contact time between naphtha and the catalyst in a range of 1 to 3 s.
 13. The method of any of claim 1, wherein the reaction conditions include an operation pressure in a range of 100 to 300 Pa.
 14. The method of any claim 1, wherein the method has a methane yield of less than 10%.
 15. The method of claim 3, wherein the method has a methane yield of less than 10%.
 16. The method of claim 4, wherein the method has a methane yield of less than 10%.
 17. The method of claim 5, wherein the method has a methane yield of less than 10%.
 18. The method of claim 6, wherein the method has a methane yield of less than 10%.
 19. The method of claim 7, wherein the method has a methane yield of less than 10%.
 20. The method of claim 8, wherein the method has a methane yield of less than 10%. 